Room-temperature vertical-cavity surface-emitting lasers at 4 μm with GaSb-based type-II quantum wells

We report electrically pumped λ = 4 μm vertical-cavity surface-emitting lasers (VCSELs) that significantly extend the wavelength range covered with electrically pumped VCSELs into the mid infrared. A single stage active region with eight type-II quantum wells provides sufficient gain, while lateral current confinement and waveguiding are accomplished with the proven buried tunnel junction technology. These devices operate in continuous wave (CW) up to −7 °C and in pulsed operation up to 45 °C. Their CW threshold pump power levels are below 10 mW at temperatures well accessible by thermo-electric cooling, and their maximum single-mode output power is around 0.18 mW. Single-mode operation with side-mode suppression ratio of more than 20 dB and a continuous electro-thermal tuning range as large as 19.2 nm are achieved.